Projection method for measuring the inner contours of wire drawing dies



wy w48. 23,444,539. f

F. C. ELDER PROJECTION METHOD FOR 'MEASURING THE INNER CONTOURS OF WIREDRAWING DIES Filed March 1l, 1944 More specically, the apparatusincludes aA light source I in the form of an electric arc, means 2 forholding the wire drawing die 3 with its die-hole entrance spaced fromvthe source I in substantial alignment therewith, and a light projectionscreen positioned opposite the exit of the die hole at a known angle toits axis when the die 3 is held by the means 2.v The lightsource I issufficiently spacedfrom the entrance of the die 3 so that the light isprojected into this entrance substantially parallel the die-hole axis,it having been found in practical work that parallelism is approachedsufciently, with such an arrangement, to render unnecessary the need forcondensing lenses with theirv attendant cooling Aand cleaning problems,it being understood that the light source I must radiate lightwlthconsiderable intensity, particularly when the die hole Whose contouris being examined is of the smaller diameters used in drawing ne wire.,For obvious reasons, the light source I is enclosed in a housing 5, andthis housing is preferably provided with an optical tube 6 in the end ofwhich is mounted a diaphragm plate l having an aperture 8 forrestricting the light radiated from the light source, to the die 3,approximately to the amount required to just about cover the entireperiphery of the smoothing-out section ofthe die hole, this being intheinterest of-.preventing undue heating of the die. The plate l isremovable so that other plates may be substituted having suitably shapedapertures 8 for various sizes of dies. An iris diaphragm may be used butit introduces complications in its operation due to the heating itreceives andthe dirt with which it is apt to be contaminated in milluse' of the apparatus. y

The means 2 is illustrated as being a simple rest having downwardlytapering surfaces 9 in which the periphery of the die 3 rests and asurface I0 normal the surfaces 9 and which provides a bearing surfacelfor engaging the dieholder bearing face of the die 3, around its dieholeexit, and holding'this. bearing face normal the direction the light isprojected `from the source I into the die-hole entrance. Rotation of thedie 3 may be accomplished by manually turning the die, the surfaces 9,engaging the die periphery, tapering so the die may be rotated about itsaxis properly, providing the die outside periphery is concentric to thedie-hole axis, which this periphery should be in a properly made die.The surface Ill, against which the die may be held flatly, serves tofurther steady the die during its rotation providing the dies die-holderbearing surface is normal the die axis, which it also should bein aproperly made die. 1

In connection Awith the foregoing, it is to be understood that the die 3is shown as a tungsten carbide die of the type having the tungstencarbide nib incased in a steel shell having a cylindrical exterior and aface surrounding the diehole exit which should be truly at right anglesto this periphery and to the die-hole axis, while the cylindricalperiphery should be truly cylindrical about this axis, if the die isproperly made. Such dies are used for drawing ne wire sizes and have thesmaller diameters which heretofore presented the most dimculty inproperly meas--A uring their die-hole inside contours.

The .die holder 3 is shown as having a mounting Il, permitting itsvertical adjustment, which is carried by a slide i2 working on a slidebar I3 which also carries the housing 5 for the light source I, theslide-bar arrangement being likethat conventionally used in the case ofoptical instruments.

I The light projection screen 4 is removably mounted by a' screen holderI 4 which is itself held normal the optical axis of the apparatus by aslide i5 working on the slide bar I3, the known angle between the screenand die-hole axis being a right angle yin this instance. The screenAllis shown as being adapted to be slid laterally into the holder I4,and the latter is in the formof a frame permitting free light passagewhen the screen 4 is removed.

In using the apparatus as it has been described so. far, the die 3 issettled snugly into the down.

wardly tapering surfaces or V-shaped portion il of the die holding means2, with its die-hole entrance facing the light source l and its die.

holder bearing surface atly positioned against thesurface Iii of the dieholding means 2. As

' suming the light source I to be in operation, light is projectedtherefrom through the aperture 8 and onto the die 3, the die holdingmeans being adjusted vertically by use of its mounting I I until thebeamof light projected through the aperture 8 of the diaphragm plate 'Iregisters with" pears, on the light projecting screen 4, surround-f edby an annulus of light formed by the reflected:

light from the smoothing-out section of the die hole. If the die isproperly positioned, the disk of light should be vertically midwaybetween the light annulus, which may beascertained byv di` rectmeasurement, but if it is not the die holding means 2 may be raised orlowered as required to effect this relative positioning. Once the lightdisk is positioned vertically exactly intermediate the light annulus,Athe die hole is in optical align-- ment axially with the light source I,it being understood that the die holding means 2 is preciselyconstructed for horizontal positioning of the die 3 with its die-holeaxis in proper` horizontal alignment with the light source I.

If at this time the disk of light is not horizontally midway theextremes of the light annulus, itis :because either the bearing, surfaceor smoothing-lout section of the die lacks con-centrieity either lwitheach other or with the dies cylindrical exterior. Manual rotation of thedie in the die holding means serves to answer the questions thusintroduced, shifting of the light disk formed, by the unreflectedlightindicating lack of concentricity of the die-hole inside contour,generally, with the cylindrical die outside, whereas if this diskremains fixed in position. during die rotation, but the light annulusvaries in position,

est. .1,

tion respecting the die-hole axis is indicated. Furthermore, if the dieholder bearing face around the die-hole exit is kept nrrnly pressedagainst the surface l of the dic holding lrneans 2 during rotation ofthe die 3, and the position of the light disk on the screen 4 shifts, itbecomes obvious that this bearing face ci the die is not normal thedie-hole axis as it should be. Therefore, by resorting to these variousmanipulations it becomes possible to quickly and accurately determinewhether the various die parts are in their proper relativerelationships. f

The apparatus illustrated by Figure l also includes a second lightprojection screen holder IB constructed the same as the screen holderlll and provided with a slide ll working on the slide bar Sincev thelight annulus appearing on the screen 4 while it is in the holder i4,and which is formed by the reiiected light from the' die-holesmoothing-out section, represents a conical light annulus whose conicalangularity is fixed by the angularity 'of the die-hole smoothing-outsection, it

becomes possible, by measuring the conical angularity of this conicalannulus, to determine the angularity of this smoothing-out section. Thisis done by positioning the projection screen holders i4 and i6 so as tohold the projection screen 4 at two positions spuaced apart a knowndistance beyond the die-hold exit of the die 3,

and by then measuring either the diierent diameters of the light annulithat appear on the screen in its two positions, or the distance betweenthe light disk that appears on the screen in both positions and thedifferent distances between this light disk andthe light annuli thatappear in both positions, to then, by Vsimple trigonometry, :meas` beingshown at 3d. The substantially parallel lighty coming from the lightsource I is legended as is the reiiected light and the nonrefiectedlight respectively forming the light annnli and-the light disk. Thelight is being projected in a direction substantially parallel thedie-hole axis, so its direction is known relative thereto, and hassufcient coverage to impinge on the entire periphery @of thesmoothing-out section 3, from which it is reflected to the screen d, thenonreiiected light passing directly to this screen. When the screen 4 ispositioned by the screen holder i4 the distance Dl diametrically betweenthe inner periphery of the light annulus appearing thereon is measured,and the screen 4 is then shifted to the holder IB and the same distanceremeasured, or the screen l m-ay be removed and another screen 4aalready in place in the holder I6 used to receive the light annuluswhich is now of the greater diameter D2. The distance between the twoscreen positions being known, half the difference between the Values DIfrom D2, i. e. the amount of the change in the radius of the image,provides the now known base b of a right triangle having an altitude aequaling the known distance between the two screen positions, 'and withits hypotenuse c and altitude a deining the angle B, the value of whichcan easily be solved by trigonometry and which has the same value as theentrance angle of the smoothing-out section of the die hole. It is to beremembered that the direction of the incident light respecting thedie-hole axis is known, it being substantially parallel thereto in thecase of the apparatus disclosed, that the screen l is positioned by boththe holders I4 and IB normal the die-hole axis so its angularityrespecting this axis is known, and that the distance between the twoscreen positions is known. If the angle oi taper of the smoothing-outsection is desired, it maybe obtained simply by dividing by two thevalue tof the angle B when it is calculated.

When the relatively spaced positions of the light source, die and screenremain fixed, it is possible to calibrate the screen so that it isunnecessary to inconvenience the operator by making him resort totrigonometric calculations. That is to say, in such an instance thediameter of the light annulus and the position of any portion of thesame on the screen is a direct result of the angularity of thesmoothing-out section, so ob,

lservation of the position of any portion lof the light annulus on ascreen that has previously been calibrated provides for direct readingof the value of this angularity, since it provides for directlymeasuring the angularity between the light projecting direction and theprojecting direction of the reflected light, with lcorrection for anyangularity between the nrst` direction and the die-hole axis if suchexists.

I claim: A method including projecting light through the entrance of thedie hole of a wire drawing die `substantially parallel the die hole axisionto the periphery of the die hole smoothing-out section and throughthe die hole bearing surface section, spacing a light projection screenbeyond the exit of said die hole at a right angle to its axis, measuringthe image projected on said screen by the reflected light emitting fromthe exit of said die hfole, altering the initial spacing between theexit of said die hole and said screen a known amount while maintainingthe said angularity between the die hole axis and said screen, measuringthe image projected on said screen when` located in said secondposition, the amount of the change in the radius of said image resultingfrom altering the spacing between the exit of the die hole andy screenforming the base of a right triangle, the altitude of said trianglebeing the Said known amount of the altering of the spacing between f theexit of the die hole and the screen, and deof said die.

termining the included angle between the altitude and hypotenuse of thesaid triangle to de-` termine the angle Pof the smoothing-out sectionELINT' C.4 ELDER.

REFERENCES CEDy The following references are of record in the le of thispatent:

UNITED STATES PATENTS e i f* L s

